Candidate miRNAs in human breast cancer biomarkers: a systematic review

Breast cancer (BC) is the most prevalent cancer and the main cause of cancer deaths among females around the world. For early diagnosis of BC, there would be an immediate and essential requirement to search for sensitive biomarkers. To identify candidate miRNA biomarkers for BC, we performed a general systematic review regarding the published miRNA profiling researches comparing miRNA expression level between BC and normal tissues. A miRNA ranking system was selected, which considered frequency of comparisons in direction and agreement of differential expression. We determined that two miRNAs (mir-21 and miR-210) were upregulated consistently and six miRNAs (miR-145, miR-139-5p, miR-195, miR-99a, miR-497 and miR-205) were downregulated consistently in at least three studies. MiR-21 as the most consistently reported miRNA was upregulated in six profiling studies. Although these miRNAs require being validated and further investigated, they could be potential candidates for BC miRNA biomarkers and used for early prognosis or diagnosis.